Thread connections for oil field tubular goods have been either of the tapered or cylindrical thread type. The tapered threaded connections generally deform the interengaged threads on make-up which creates a radial interference in the connection to resist inadvertent disengagement of the threads. Cylindrical threads are often provided with free running radial clearance threads, usually in two steps, which enabled repeated make-up of the thread connectors using torque make-up shoulders without deforming the threads and which substantially eliminate the radial interference induced hoop stress. Examples of such cylindrical thread connectors are disclosed in U.S. Pat. Nos. 2,907,589 and 2,992,019, along with others, which are assigned to the assignee of the present invention.
When the radial clearance cylindrical thread connectors are subjected to tensile loading, there appears to be a reduction in the "break out" torque needed to separate the pin and box members. This loss or reduction in break out torque may enable inadvertent separation of the connection as a result of well conditions such as vibration and could result in tubing leak, dropping the string or a well blowout.